Condensed Consolidated Statements of Changes in Shareholder's Equity (USD $) In Millions, unless otherwise specified	Total USD ($)	Common Stock	Additional Paid-In Capital USD ($)	Accumulated Other Comprehensive Income (Loss) USD ($)	Retained Earnings (Deficit) USD ($)
Balance at Dec. 31, 2010 (Scenario, Previously Reported [Member])	$ 3,458.3		$ 4,326.0	$ 304.5	$ (1,175.0)
Balance (Restatement Adjustment [Member])	3,092.1		4,326.0	390.6	(1,627.3)
Shares, Outstanding at Dec. 31, 2010 (Scenario, Previously Reported [Member])		2.8
Shares, Outstanding (Restatement Adjustment [Member])		2.8
Increase (Decrease) in Stockholders' Equity
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets (Scenario, Previously Reported [Member]) (Deferred policy acquisition costs [Member])	(366.2)			64.8	(431.0)
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets (Scenario, Previously Reported [Member]) (Actuarial gains (losses) for pension and post-retirement benefit plans [Member])				21.3	(21.3)
Other comprehensive income, net of tax
Net income	87.4
Net income (Restatement Adjustment [Member])	87.4				87.4
Other comprehensive income, after tax	(12.7)
Other comprehensive income, after tax (Restatement Adjustment [Member])	(12.7)			(12.7)
Total comprehensive income	74.7
Total comprehensive income (Restatement Adjustment [Member])	74.7
Contribution of capital (Restatement Adjustment [Member])	201.0		201.0
Employee related benefits (Restatement Adjustment [Member])	0.2		0.2
Balance (Restatement Adjustment [Member])	3,368.0		4,527.2	377.9	(1,539.9)
Shares, Outstanding (Restatement Adjustment [Member])		2.8
Balance (Restatement Adjustment [Member])	3,976.3		4,533.0	747.5	(1,307.0)
Balance at Dec. 31, 2011	3,976.3
Shares, Outstanding (Restatement Adjustment [Member])		2.8
Other comprehensive income, net of tax
Net income	144.0
Net income (Restatement Adjustment [Member])	144.0				144.0
Other comprehensive income, after tax	(40.3)
Other comprehensive income, after tax (Restatement Adjustment [Member])	(40.3)			(40.3)
Total comprehensive income	103.7
Total comprehensive income (Restatement Adjustment [Member])	103.7
Employee related benefits (Restatement Adjustment [Member])	23.9		23.9
Balance (Restatement Adjustment [Member])	4,103.9		4,556.9	707.2	(1,163.0)
Balance at Mar. 31, 2012	$ 4,103.9
Shares, Outstanding (Restatement Adjustment [Member])		2.8